/* ============================================
   LinkedIn Game Solvers - Modern Theme
   ============================================ */

/* --- CSS Custom Properties (Design Tokens) --- */
:root {
    /* LinkedIn Brand Colors */
    --linkedin-blue: #0a66c2;
    --linkedin-blue-hover: #004182;
    --linkedin-blue-light: #70b5f9;
    --linkedin-green: #057642;
    --linkedin-amber: #915907;
    
    /* Light Theme (Default) */
    --color-background: #f3f2ef;
    --color-surface: #ffffff;
    --color-surface-hover: #f9fafb;
    --color-surface-active: #e8f4fd;
    --color-border: #e0dfdc;
    --color-border-strong: #c4c3c0;
    --color-text-primary: #191919;
    --color-text-secondary: #666666;
    --color-text-tertiary: #8f8f8f;
    --color-text-inverse: #ffffff;
    --color-accent: var(--linkedin-blue);
    --color-accent-hover: var(--linkedin-blue-hover);
    --color-accent-light: #e8f4fd;
    --color-success: #057642;
    --color-success-light: #d4edda;
    --color-warning: #915907;
    --color-warning-light: #fff3cd;
    --color-error: #cc1016;
    --color-error-light: #f8d7da;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.08), 0 2px 4px -1px rgba(0, 0, 0, 0.04);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
    --shadow-inner: inset 0 2px 4px rgba(0, 0, 0, 0.06);
    
    /* Grid Colors */
    --grid-cell-bg: var(--color-surface);
    --grid-cell-border: var(--color-border);
    --grid-cell-hover: var(--color-surface-hover);
    --grid-cell-selected: var(--color-accent-light);
    /* Zip blocks (edge barriers) color - distinct from numbered tile borders */
    --zip-block-color: var(--color-error);
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-full: 9999px;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
    --transition-slow: 350ms ease;
    
    /* Typography */
    --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.875rem;
    --font-size-md: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 2rem;
    --font-weight-normal: 400;
    --font-weight-medium: 500;
    --font-weight-semibold: 600;
    --font-weight-bold: 700;
    --line-height-tight: 1.25;
    --line-height-normal: 1.5;
    --line-height-relaxed: 1.75;
}

/* --- Dark Theme --- */
[data-theme="dark"] {
    --color-background: #1b1f23;
    --color-surface: #283038;
    --color-surface-hover: #323b44;
    --color-surface-active: #1a3a4f;
    --color-border: #3d4a54;
    --color-border-strong: #566470;
    --color-text-primary: #f5f5f5;
    --color-text-secondary: #b0b0b0;
    --color-text-tertiary: #808080;
    --color-text-inverse: #191919;
    --color-accent: #70b5f9;
    --color-accent-hover: #9cccfc;
    --color-accent-light: #1a3a4f;
    --color-success: #44b78b;
    --color-success-light: #1a3d2e;
    --color-warning: #f5c75d;
    --color-warning-light: #3d3520;
    --color-error: #f5756c;
    --color-error-light: #3d2020;
    
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -1px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -2px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.4), 0 10px 10px -5px rgba(0, 0, 0, 0.3);
    --shadow-inner: inset 0 2px 4px rgba(0, 0, 0, 0.3);
    
    --grid-cell-bg: var(--color-surface);
    --grid-cell-border: var(--color-border);
    --grid-cell-hover: var(--color-surface-hover);
    --grid-cell-selected: var(--color-accent-light);
}

/* --- Base Styles --- */
*, *::before, *::after {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-md);
    line-height: var(--line-height-normal);
    color: var(--color-text-primary);
    background-color: var(--color-background);
    margin: 0;
    padding: 0;
    min-height: 100vh;
    transition: background-color var(--transition-normal), color var(--transition-normal);
    display: flex;
    flex-direction: column;
}

/* --- Header & Navigation --- */
header {
    background-color: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow-sm);
}

.header-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-sm) var(--spacing-lg);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--spacing-md);
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    text-decoration: none;
    color: var(--color-text-primary);
}

.logo-icon {
    width: 36px;
    height: 36px;
    background: linear-gradient(135deg, var(--linkedin-blue), var(--linkedin-blue-hover));
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: var(--font-weight-bold);
    font-size: var(--font-size-lg);
}

.logo-text {
    font-weight: var(--font-weight-bold);
    font-size: var(--font-size-lg);
    display: none;
}

@media (min-width: 640px) {
    .logo-text {
        display: block;
    }
}

nav {
    display: flex;
    gap: var(--spacing-xs);
    flex-wrap: wrap;
    justify-content: center;
}

.tab-button {
    position: relative;
    padding: var(--spacing-sm) var(--spacing-md);
    border: none;
    background-color: transparent;
    color: var(--color-text-secondary);
    cursor: pointer;
    font-family: inherit;
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.tab-button:hover {
    background-color: var(--color-surface-hover);
    color: var(--color-text-primary);
}

.tab-button:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 2px;
}

.tab-button.active {
    color: var(--color-accent);
    background-color: var(--color-accent-light);
    font-weight: var(--font-weight-semibold);
}

.tab-button.active::after {
    content: '';
    position: absolute;
    bottom: -1px;
    left: 50%;
    transform: translateX(-50%);
    width: 60%;
    height: 3px;
    background-color: var(--color-accent);
    border-radius: var(--radius-full);
}

/* --- Theme Toggle --- */
.header-actions {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.theme-toggle {
    position: relative;
    width: 52px;
    height: 28px;
    background-color: var(--color-border-strong);
    border-radius: var(--radius-full);
    border: none;
    cursor: pointer;
    padding: 2px;
    transition: background-color var(--transition-fast);
}

.theme-toggle:hover {
    background-color: var(--color-accent);
}

.theme-toggle:focus-visible {
    outline: 2px solid var(--color-accent);
    outline-offset: 2px;
}

.theme-toggle-track {
    position: absolute;
    inset: 2px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 6px;
    font-size: 12px;
}

.theme-toggle-thumb {
    position: absolute;
    top: 2px;
    left: 2px;
    width: 24px;
    height: 24px;
    background-color: var(--color-surface);
    border-radius: 50%;
    box-shadow: var(--shadow-md);
    transition: transform var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
}

[data-theme="dark"] .theme-toggle-thumb {
    transform: translateX(24px);
}

/* --- Main Content --- */
main {
    max-width: 900px;
    margin: 0 auto;
    padding: var(--spacing-lg);
    flex: 1;
    width: 100%;
}

.game-solver {
    display: none;
    animation: fadeIn var(--transition-normal);
}

.game-solver.active {
    display: block;
}

/* --- Solver Card --- */
.solver-card {
    background-color: var(--color-surface);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    overflow: hidden;
    transition: box-shadow var(--transition-normal);
}

.solver-card:hover {
    box-shadow: var(--shadow-lg);
}

.solver-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-lg);
    border-bottom: 1px solid var(--color-border);
    background: linear-gradient(135deg, var(--color-accent-light), transparent);
}

.solver-title {
    margin: 0;
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-bold);
    color: var(--color-text-primary);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.solver-title-icon {
    font-size: var(--font-size-2xl);
}

.play-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-xs) var(--spacing-md);
    background-color: var(--color-accent);
    color: var(--color-text-inverse);
    text-decoration: none;
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    border-radius: var(--radius-full);
    transition: all var(--transition-fast);
}

.play-link:hover {
    background-color: var(--color-accent-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.play-link svg {
    width: 14px;
    height: 14px;
}

.solver-body {
    padding: var(--spacing-lg);
}

/* --- Solver Layout --- */
.solver-layout {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

@media (min-width: 640px) {
    .solver-layout {
        flex-direction: row;
    }
}

/* --- Controls Panel --- */
.controls-panel {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
    min-width: 150px;
}

.controls-panel label {
    display: block;
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-xs);
}

.controls-panel input[type="range"] {
    width: 100%;
    height: 6px;
    appearance: none;
    -webkit-appearance: none;
    background: var(--color-border);
    border-radius: var(--radius-full);
    cursor: pointer;
}

.controls-panel input[type="range"]::-webkit-slider-thumb {
    appearance: none;
    -webkit-appearance: none;
    width: 18px;
    height: 18px;
    background: var(--color-accent);
    border-radius: 50%;
    cursor: pointer;
    transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.controls-panel input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.1);
    box-shadow: 0 0 0 4px var(--color-accent-light);
}

.controls-panel input[type="range"]::-moz-range-thumb {
    width: 18px;
    height: 18px;
    background: var(--color-accent);
    border: none;
    border-radius: 50%;
    cursor: pointer;
}

.size-label {
    display: inline-block;
    font-weight: var(--font-weight-semibold);
    color: var(--color-accent);
    margin-left: var(--spacing-xs);
}

.button-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.controls-panel button {
    position: relative;
    padding: var(--spacing-sm) var(--spacing-lg);
    border: none;
    border-radius: var(--radius-md);
    font-family: inherit;
    font-size: var(--font-size-md);
    font-weight: var(--font-weight-semibold);
    cursor: pointer;
    transition: all var(--transition-fast);
    overflow: hidden;
}

.btn-primary {
    background: linear-gradient(135deg, var(--color-accent), var(--color-accent-hover));
    color: var(--color-text-inverse);
    box-shadow: var(--shadow-sm);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-primary:active {
    transform: translateY(0);
}

.btn-secondary {
    background-color: var(--color-surface);
    color: var(--color-text-primary);
    border: 1px solid var(--color-border);
}

.btn-secondary:hover {
    background-color: var(--color-surface-hover);
    border-color: var(--color-border-strong);
}

/* Button ripple effect */
.controls-panel button::after {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(circle, rgba(255,255,255,0.3) 0%, transparent 70%);
    opacity: 0;
    transform: scale(0);
    transition: opacity 0.3s, transform 0.3s;
}

.controls-panel button:active::after {
    opacity: 1;
    transform: scale(2);
    transition: 0s;
}

/* --- Grid Panel --- */
.grid-panel {
    flex: 1;
    display: flex;
    justify-content: center;
    align-items: flex-start;
}

.grid-container {
    display: grid;
    gap: 1px;
    padding: 0;
    background-color: var(--color-border);
    border-radius: var(--radius-md);
    border: 3px solid var(--color-border-strong);
    box-shadow: 
        0 4px 6px -1px rgba(0, 0, 0, 0.15),
        0 2px 4px -1px rgba(0, 0, 0, 0.1),
        0 0 0 1px rgba(0, 0, 0, 0.05);
    overflow: hidden;
}

[data-theme="dark"] .grid-container {
    box-shadow: 
        0 4px 6px -1px rgba(0, 0, 0, 0.4),
        0 2px 4px -1px rgba(0, 0, 0, 0.3),
        0 0 0 1px rgba(255, 255, 255, 0.05);
}

.grid-cell {
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: var(--grid-cell-bg);
    font-size: var(--font-size-lg);
    font-weight: var(--font-weight-medium);
    color: var(--color-text-primary);
    transition: all var(--transition-fast);
    cursor: default;
    user-select: none;
}

/* --- Instructions Card --- */
.instructions {
    margin-top: var(--spacing-lg);
    padding: var(--spacing-lg);
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    border-left: 4px solid var(--color-accent);
}

.instructions-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
    cursor: pointer;
}

.instructions h3 {
    margin: 0;
    font-size: var(--font-size-md);
    font-weight: var(--font-weight-semibold);
    color: var(--color-text-primary);
}

.instructions-icon {
    font-size: var(--font-size-lg);
}

.instructions ol,
.instructions ul {
    margin: 0;
    padding-left: var(--spacing-lg);
    color: var(--color-text-secondary);
}

.instructions li {
    margin-bottom: var(--spacing-sm);
    line-height: var(--line-height-relaxed);
}

.instructions li:last-child {
    margin-bottom: 0;
}

.instructions p {
    margin: 0 0 var(--spacing-sm) 0;
    color: var(--color-text-secondary);
}

.instructions strong {
    color: var(--color-text-primary);
}

/* ============================================
   Game-Specific Styles
   ============================================ */

/* --- Zip Solver --- */
#zip-grid {
    gap: 1px;
    background-color: var(--color-border);
}

#zip-grid .grid-cell {
    cursor: pointer;
}

#zip-grid .grid-cell:hover {
    background-color: var(--grid-cell-hover);
}

#zip-grid .grid-cell.user-selected {
    background-color: var(--color-accent-light);
    color: var(--color-accent);
    font-weight: var(--font-weight-bold);
    box-shadow: inset 0 0 0 2px var(--color-accent);
}

#zip-grid .grid-cell.zip-solution-cell {
    font-weight: var(--font-weight-semibold);
    color: var(--color-text-primary);
    transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

#zip-grid .grid-cell.zip-solution-cell:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

#zip-grid .grid-cell.zip-solution-start {
    box-shadow: inset 0 0 0 3px var(--color-accent);
}

#zip-grid .grid-cell.zip-solution-end {
    box-shadow: inset 0 0 0 3px var(--color-success);
}

/* --- Tango Solver --- */
#tango-grid {
    position: relative;
    display: grid;
    grid-template-columns: repeat(11, auto);
    grid-template-rows: repeat(11, auto);
    gap: 0;
    width: fit-content;
    padding: var(--spacing-xs);
    background-color: var(--color-border);
    border-radius: var(--radius-md);
    border: 3px solid var(--color-border-strong);
    box-shadow: 
        0 4px 6px -1px rgba(0, 0, 0, 0.15),
        0 2px 4px -1px rgba(0, 0, 0, 0.1),
        0 0 0 1px rgba(0, 0, 0, 0.05);
    user-select: none;
    overflow: hidden;
}

[data-theme="dark"] #tango-grid {
    box-shadow: 
        0 4px 6px -1px rgba(0, 0, 0, 0.4),
        0 2px 4px -1px rgba(0, 0, 0, 0.3),
        0 0 0 1px rgba(255, 255, 255, 0.05);
}

#tango-grid .grid-cell {
    display: flex;
    justify-content: center;
    align-items: center;
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    user-select: none;
}

#tango-grid .grid-cell.symbol-cell {
    width: 56px;
    height: 56px;
    background-color: var(--grid-cell-bg);
    border-radius: var(--radius-sm);
    font-size: 1.8em;
    cursor: pointer;
    transition: all var(--transition-fast);
}

#tango-grid .grid-cell.symbol-cell:hover {
    background-color: var(--grid-cell-hover);
}

#tango-grid .grid-cell.horizontal-constraint {
    width: 16px;
    height: 56px;
    font-size: 1em;
    cursor: pointer;
    background-color: transparent;
    border-radius: var(--radius-xs);
    transition: all var(--transition-fast);
}

#tango-grid .grid-cell.vertical-constraint {
    width: 56px;
    height: 16px;
    font-size: 1em;
    cursor: pointer;
    background-color: transparent;
    border-radius: var(--radius-xs);
    transition: all var(--transition-fast);
}

#tango-grid .grid-cell.diagonal-space {
    width: 16px;
    height: 16px;
    background-color: var(--color-border-strong);
    border-radius: var(--radius-xs);
    cursor: default;
}

#tango-grid .grid-cell.sun-cell {
    background: linear-gradient(135deg, #fff9db, #fff3b0);
    box-shadow: inset 0 0 0 2px #f0c000;
}

[data-theme="dark"] #tango-grid .grid-cell.sun-cell {
    background: linear-gradient(135deg, #4a4020, #3d3518);
    box-shadow: inset 0 0 0 2px #c9a000;
}

#tango-grid .grid-cell.moon-cell {
    background: linear-gradient(135deg, #e8eaff, #d4d8ff);
    box-shadow: inset 0 0 0 2px #6366f1;
}

[data-theme="dark"] #tango-grid .grid-cell.moon-cell {
    background: linear-gradient(135deg, #2a2d50, #232640);
    box-shadow: inset 0 0 0 2px #818cf8;
}

#tango-grid .grid-cell.equal-constraint {
    background-color: var(--color-success-light);
    color: var(--color-success);
    font-weight: var(--font-weight-bold);
}

#tango-grid .grid-cell.opposite-constraint {
    background-color: var(--color-error-light);
    color: var(--color-error);
    font-weight: var(--font-weight-bold);
}

/* --- Queens Solver --- */

/* Color Palette */
.color-palette {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    padding: var(--spacing-sm);
    background-color: var(--color-surface-hover);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
    max-width: 180px;
}

.color-swatch {
    width: 28px;
    height: 28px;
    border-radius: var(--radius-sm);
    border: 2px solid transparent;
    cursor: pointer;
    transition: all var(--transition-fast);
    position: relative;
    overflow: visible;
}

.color-swatch:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-md);
}

.color-swatch.active {
    border-color: var(--color-text-primary);
    box-shadow: 0 0 0 2px var(--color-surface), 0 0 0 4px var(--color-text-primary);
    transform: scale(1.1);
}

.swatch-check {
    position: absolute;
    top: 0px;
    left: 0px;
    width: 18px;
    height: 18px;
    border-radius: var(--radius-full);
    background-color: var(--color-surface);
    color: var(--color-text-primary);
    border: 2px solid var(--color-text-primary);
    display: none;
    align-items: center;
    justify-content: center;
    font-size: 12px;
    font-weight: var(--font-weight-bold);
    box-shadow: var(--shadow-sm);
    z-index: 10;
}

.swatch-check::before {
    content: '\2713';
}

.swatch-check.visible {
    display: flex;
}

.color-swatch.eraser {
    background-color: var(--color-surface);
    border: 2px dashed var(--color-border-strong);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    color: var(--color-text-secondary);
}

.color-swatch.eraser:hover {
    border-color: var(--color-error);
    color: var(--color-error);
}

.color-swatch.eraser.active {
    border-style: solid;
    border-color: var(--color-error);
    color: var(--color-error);
    box-shadow: 0 0 0 2px var(--color-surface), 0 0 0 4px var(--color-error);
}

#queens-grid {
    gap: 1px;
    background-color: var(--color-border);
}

#queens-grid .grid-cell {
    cursor: pointer;
    transition: all var(--transition-fast);
}

#queens-grid .grid-cell:hover {
    filter: brightness(0.95);
}

#queens-grid .grid-cell.queen-placed {
    font-weight: var(--font-weight-bold);
    font-size: 1.4em;
    color: var(--color-text-primary);
}

#queens-grid .grid-cell.solved-queen {
    font-weight: var(--font-weight-bold);
    font-size: 1.4em;
    color: var(--color-text-primary);
    text-shadow: 0 0 4px rgba(255, 255, 255, 0.8);
}

/* --- Mini Sudoku Solver --- */
#mini-grid {
    display: grid;
    grid-template-columns: repeat(6, 48px);
    grid-template-rows: repeat(6, 48px);
    gap: 0;
    padding: 0;
    background-color: var(--grid-cell-bg);
    border-radius: var(--radius-md);
    border: 3px solid var(--color-border-strong);
    box-shadow: 
        0 4px 6px -1px rgba(0, 0, 0, 0.15),
        0 2px 4px -1px rgba(0, 0, 0, 0.1),
        0 0 0 1px rgba(0, 0, 0, 0.05);
    user-select: none;
    overflow: hidden;
}

[data-theme="dark"] #mini-grid {
    box-shadow: 
        0 4px 6px -1px rgba(0, 0, 0, 0.4),
        0 2px 4px -1px rgba(0, 0, 0, 0.3),
        0 0 0 1px rgba(255, 255, 255, 0.05);
}

#mini-grid .grid-cell {
    cursor: pointer;
    font-size: var(--font-size-lg);
    font-weight: var(--font-weight-medium);
    background-color: var(--grid-cell-bg);
    transition: all var(--transition-fast);
    /* Borders will be set by JS with CSS variable colors */
}

#mini-grid .grid-cell:hover {
    background-color: var(--grid-cell-hover);
}

#mini-grid .grid-cell.mini-user-cell {
    background-color: var(--color-accent-light);
    font-weight: var(--font-weight-semibold);
    color: var(--color-accent);
}

#mini-grid .grid-cell.mini-solved-cell {
    background-color: var(--color-success-light);
    color: var(--color-success);
    font-weight: var(--font-weight-semibold);
}

#mini-grid .grid-cell.mini-error-cell {
    background-color: var(--color-error-light);
    color: var(--color-error);
    font-weight: var(--font-weight-semibold);
}

#mini-grid.mini-locked {
    pointer-events: none;
    opacity: 0.95;
}

/* --- Number Picker --- */
.mini-number-picker {
    position: absolute;
    display: none;
    grid-template-columns: repeat(3, 44px);
    grid-auto-rows: 44px;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm);
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    z-index: 1000;
}

.mini-number-picker.visible {
    display: grid;
}

.mini-number-picker button {
    width: 44px;
    height: 44px;
    border: none;
    border-radius: var(--radius-md);
    background-color: var(--color-surface-hover);
    color: var(--color-text-primary);
    font-weight: var(--font-weight-bold);
    font-size: var(--font-size-md);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.mini-number-picker button:hover {
    background-color: var(--color-accent-light);
    color: var(--color-accent);
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

.mini-number-picker button:active {
    transform: translateY(0);
}

.mini-number-picker .mini-number-clear {
    grid-column: 1 / -1;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--color-error-light);
    color: var(--color-error);
}

.mini-number-picker .mini-number-clear:hover {
    background-color: var(--color-error);
    color: var(--color-text-inverse);
}

/* ============================================
   Footer
   ============================================ */
footer {
    display: none;
}

/* ============================================
   Animations
   ============================================ */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.6;
    }
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(-10px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

/* ============================================
   Utility Classes
   ============================================ */
.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

.text-center {
    text-align: center;
}

.mt-md {
    margin-top: var(--spacing-md);
}

.mb-md {
    margin-bottom: var(--spacing-md);
}

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 640px) {
    .header-container {
        padding: var(--spacing-sm);
    }
    
    .tab-button {
        padding: var(--spacing-xs) var(--spacing-sm);
        font-size: var(--font-size-xs);
    }
    
    main {
        padding: var(--spacing-md);
    }
    
    .solver-header {
        flex-direction: column;
        gap: var(--spacing-sm);
        text-align: center;
    }
    
    .solver-body {
        padding: var(--spacing-md);
    }
    
    .grid-container {
        transform: scale(0.85);
        transform-origin: top center;
    }
    
    #tango-grid .grid-cell.symbol-cell {
        width: 44px;
        height: 44px;
        font-size: 1.4em;
    }
    
    #tango-grid .grid-cell.horizontal-constraint {
        width: 12px;
        height: 44px;
    }
    
    #tango-grid .grid-cell.vertical-constraint {
        width: 44px;
        height: 12px;
    }
    
    #tango-grid .grid-cell.diagonal-space {
        width: 12px;
        height: 12px;
    }
}